Has anybody checked, or could anybody test, if the Katana can output sound from two different sources simultaneously? like USB and Optical, for example, like the Astro A50 or Steelseries 840 headsets. I use Astro A50 as it fits that need currently but I'd like to take the headphones off my ears from time to time...

Your question isn't quite clear; are you looking to play from multiple input sources, or play out of the speakers while also listening on headphones?

As for input sources, you can have several hooked up at once and switch between them using the source button. For output . . . I would be surprised if you could just keep your headphones plugged in. Pretty much any speaker system mutes the speakers when headphones are plugged in. But hey, I could be wrong.

My original question was about having to different audio sources, such as optical and usb playing simultaneously through the katana. This works on the Astro A50 headphones, which I will continue to need to use regardless.

You, however, bring up a good point; It'd be nice if there were an optical out, for example, to connect to the Astro A50s, but at least there's a regular 3.5mm headphone jack in the back; hopefully that's something I can leave plugged and continue to listen through the speakers, but I'd understand if were one or the other; ideally, I'd use the katana whenever I can make some noise, and put headphones on when I need to be quieter.

The Astro A50s do have an optical out, so I think I might be able to connect everything properly.